Microstructure and magnetic properties of bulk nanocomposite magnets prepared by crystallizing amorphous Nd3.6Pr5.4Fe80Co3B7Nb1 under high pressure

The microstructures and magnetic properties of bulk α-Fe/R2Fe14B (R = Nd, Pr) nanocomposite magnets prepared by crystallizing amorphous Nd3.6Pr5.4Fe80Co3B7Nb1 at 923 K under different pressures were studied. The average size of R2Fe14B nanocrystals decreases monotonically from 42.9 to 12.1 nm with an increase in pressure from normal pressure to 6 GPa, while that for α-Fe nanocrystals first increases from 16.9 to 24.8 nm when a pressure of 1 GPa is applied and then decreases monotonically with a further increase in pressure, and a small size of about 10 nm was obtained at a pressure of p = 6 GPa. Compared with the nanocomposite α-Fe/R2Fe14B ribbons produced by annealing the amorphous alloy under normal pressure, the bulk nanocomposite magnets prepared under high pressures have much more homogeneous microstructures and thus show enhanced magnetic properties. The effect of the pressure on the microstructures of the bulk nanocomposite magnets is discussed.